The goal of this research is to develop a clearer understanding of the impacts of changes in state laws concerning the use and possession of marijuana. The fact that some states have changed their laws about marijuana and others are about to do so, provides a group of "natural experiments". This proposal builds upon data collected in 1975 and 1976 by the larger Monitoring the Future project, thereby permitting a "before and after" assessment of the impacts of these natural experiments. The proposed work would be carried out simultaneously with the Monitoring the Future data collections, and would involve identical questionnaires and procedures. In five states where marijuana laws have recently changed there are 32 high schools for which 1975 and 1976 data exist; we propose to survey the senior classes in these schools again in 1977 and 1978. For the 1978 survey we also propose to include an additional 15 schools in two or three other states which will, by that time, have changed marijuana laws. These efforts imply target samples of about 5500 seniors in 1977 (in 32 schools), and about 8000 in 1978 (in 47 schools). The Monitoring the Future project includes fairly extensive follow-up efforts so that each graduating class can be studied longitudinally; we propose to supplement those efforts in several of the states which have changed marijuana laws. These several supplementary samples would increase the data base in states which are changing marijuana laws, thereby permitting an extensive analysis of the impact of law change on marijuana use, use of other illicit drugs, use of alcohol, attitudes toward drug use, criminal behavior, alienation, and an array of other dimensions, with a time span covering 1975 through 1978. Because the Monitoring the Future project provides data on a large national cross-section, there are rich opportunities for nationwide "control group data" for comparison with the findings from the "experimental" states.